Taper-etching method and method of manufacturing near-field light generator

ABSTRACT

A method of taper-etching a layer to be etched that is made of a dielectric material and has a top surface. The method includes the steps of: forming an etching mask with an opening on the top surface of the layer to be etched; and taper-etching a portion of the layer to be etched, the portion being exposed from the opening, by reactive ion etching so that a groove having two wall faces intersecting at a predetermined angle is formed in the layer to be etched. The step of taper-etching employs an etching gas containing a first gas contributing to the etching of the layer to be etched and a second gas contributing to the deposition of a sidewall protective film, and changes, during the step, the ratio of the flow rate of the second gas to the flow rate of the first gas so that the ratio increases.

This is a Continuation of application Ser. No. 13/353,834 filed Jan. 19,2012. The disclosure of the prior application is hereby incorporated byreference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a taper-etching method for forming agroove having a V-shaped cross section in a layer to be etched that ismade of a dielectric material, and to a method of manufacturing anear-field light generator using the taper-etching method.

2. Description of the Related Art

Recently, magnetic recording devices such as magnetic disk drives havebeen improved in recording density, and thin-film magnetic heads andrecording media of improved performance have been demanded accordingly.Among the thin-film magnetic heads, a composite thin-film magnetic headhas been used widely. The composite thin-film magnetic head has such astructure that a read head including a magnetoresistive element(hereinafter, also referred to as MR element) for reading and a writehead including an induction-type electromagnetic transducer for writingare stacked on a substrate. In a magnetic disk drive, the thin-filmmagnetic head is mounted on a slider that flies slightly above thesurface of the magnetic recording medium.

To increase the recording density of a magnetic recording device, it iseffective to make the magnetic fine particles of the recording mediumsmaller. Making the magnetic fine particles smaller, however, causes theproblem that the magnetic fine particles drop in the thermal stabilityof magnetization. To solve this problem, it is effective to increase theanisotropic energy of the magnetic fine particles. However, increasingthe anisotropic energy of the magnetic fine particles leads to anincrease in coercivity of the recording medium, and this makes itdifficult to perform data writing with existing magnetic heads.

To solve the foregoing problems, there has been proposed a technologyso-called thermally-assisted magnetic recording. The technology uses arecording medium having high coercivity. When writing data, a writemagnetic field and heat are simultaneously applied to the area of therecording medium where to write data, so that the area rises intemperature and drops in coercivity for data writing. The area wheredata is written subsequently falls in temperature and rises incoercivity to increase the thermal stability of magnetization.Hereinafter, a magnetic head for use in thermally-assisted magneticrecording will be referred to as a thermally-assisted magnetic recordinghead.

In thermally-assisted magnetic recording, near-field light is typicallyused as a means for applying heat to the recording medium. A knownmethod for generating near-field light is to use a plasmon generator,which is a piece of metal that generates near-field light from plasmonsexcited by irradiation with laser light. The laser light to be used forgenerating the near-field light is typically guided through a waveguide,which is provided in the slider, to the plasmon generator disposed neara medium facing surface of the slider.

U.S. Patent Application Publication No. 2010/0290323 A1 discloses atechnology for coupling the light that propagates through the waveguidewith the plasmon generator in surface plasmon mode via a buffer part,thereby exciting surface plasmons on the plasmon generator.

Here, a description will be given of an example of the shape of theplasmon generator and the arrangement of the plasmon generator and thewaveguide. In this example, the plasmon generator is disposed above thetop surface of the core of the waveguide. The plasmon generator has anedge part facing the top surface of the core of the waveguide. Acladding is disposed around the core. The cladding includes a portionlying between the edge part of the plasmon generator and the top surfaceof the core, and this portion of the cladding serves as the buffer part.

In the aforementioned plasmon generator, an end of the edge part locatedin the medium facing surface serves as a near-field light generatingpart. In the plasmon generator, the light that propagates through thecore is totally reflected at the top surface of the core. This causesevanescent light to occur from the top surface of the core. Then, atleast on the edge part of the plasmon generator, surface plasmons areexcited through coupling with the aforementioned evanescent light. Thesurface plasmons propagate along the edge part to reach the near-fieldlight generating part, and near-field light is generated from thenear-field light generating part based on the surface plasmons. Such aconfiguration allows the surface plasmons excited on the plasmongenerator to propagate to the near-field light generating part with highefficiency.

The aforementioned configuration can be formed in the following manner.First, a layer to be etched is formed using a dielectric material thatis to be employed for the cladding. Part of the layer to be etched islocated on the top surface of the core. Then, a groove that is V-shapedin cross section parallel to the medium facing surface (hereinafter,also referred to as V-shaped groove) is formed in the layer to beetched. This groove is formed not to reach the top surface of the core.Being provided with the groove, the layer to be etched becomes part ofthe cladding. The plasmon generator is then formed in the groove.

In the aforementioned configuration, the V-shaped groove has two wallfaces that intersect at a predetermined angle, and the plasmon generatorhas two slopes that are opposed to the two wall faces. The two slopes ofthe plasmon generator intersect each other to form the edge part of theplasmon generator. The angle between the two slopes affects theintensity of surface plasmons excited on the plasmon generator and thespot diameter of the near-field light generated from the near-fieldlight generating part. As the angle between the two slopes decreases,the edge part becomes sharper and the near-field light generated fromthe near-field light generating part decreases in spot diameter. Toincrease the intensity of the surface plasmons excited on the plasmongenerator, however, the angle between the two slopes is preferablyincreased to some extent. This means that there is a preferred range forthe angle between the two slopes. By way of example, the angle betweenthe two slopes preferably falls within the range of 50° to 120°. Theangle between the two slopes can be defined within the range of 50° to120° by allowing each of the two wall faces of the V-shaped groove toform an angle (hereinafter referred to as inclination angle) in therange of 25° to 60° with respect to the direction perpendicular to thetop surface of the layer to be etched, so that the angle between the twowall faces fall within the range of 50° to 120°.

A method for forming a V-shaped groove in a layer to be etched that willlater become part of the cladding is to taper-etch the layer to beetched by employing reactive ion etching (hereinafter, also referred toas RIE). Generally in this method, an etching gas that contains a maincomponent gas contributing to the etching of the layer to be etched anda gas for forming a sidewall protective film is used to taper-etch thelayer to be etched. The V-shaped groove is formed by allowing thesidewall protective film to get deposited on the sidewalls of the groovebeing etched. The sidewall protective film is formed of a reactionproduct produced during the etching. The inclination angle of each ofthe two wall faces of the V-shaped groove depends on the ratio of thedeposition rate of the sidewall protective film to the etching rate ofthe layer to be etched.

The aforementioned taper-etching by RIE gradually increases the depth ofthe groove being etched and gradually decreases the distance between thetwo sidewalls at the bottom of the groove. In general, as the depth ofthe groove being etched increases and the distance between the twosidewalls at the bottom of the groove decreases, in the region near thebottom of the groove the etching becomes predominant over the depositionof the sidewall protective film. Accordingly, for a V-shaped groove thatis formed by taper-etching employing the conventional RIE, theinclination angle of each of the two wall faces decreases withincreasing proximity to the lower end of the groove. As such, it hasbeen difficult with the taper-etching by the conventional RIE to form aV-shaped groove having two wall faces that each form a constant oralmost constant inclination angle from the opening to lower end of thegroove.

OBJECTS AND SUMMARY OF THE INVENTION

It is a first object of the present invention to provide a taper-etchingmethod that allows forming a groove in a layer to be etched that is madeof a dielectric material, the groove having two wall faces that eachform a constant or almost constant inclination angle from the opening tolower end of the groove and that intersect at a predetermined angle.

It is a second object of the present invention to provide a method ofmanufacturing a near-field light generator including a waveguide and aplasmon generator. The waveguide includes a core and a cladding. Thecladding includes a cladding layer having a groove located above the topsurface of the core. The groove has two wall faces that each form aconstant or almost constant inclination angle from the opening to lowerend of the groove and that intersect at a predetermined angle. Theplasmon generator has two slopes opposed to the two wall faces.According to the method, the aforementioned groove is formed in a layerto be etched that is made of a dielectric material to thereby form thecladding layer.

A taper-etching method of the present invention is a method oftaper-etching a layer to be etched. The layer to be etched is made of adielectric material and has a top surface. The method includes the stepsof: forming an etching mask on the top surface of the layer to beetched, the etching mask having an opening; and taper-etching a portionof the layer to be etched, the portion being exposed from the opening,by reactive ion etching so that a groove having two wall faces thatintersect at a predetermined angle is formed in the layer to be etched.The step of taper-etching employs an etching gas containing a first gascontributing to the etching of the layer to be etched and a second gascontributing to deposition of a sidewall protective film, and changes,during the step, the ratio of the flow rate of the second gas to theflow rate of the first gas so that the ratio increases.

A method of manufacturing a near-field light generator of the presentinvention is a method by which a near-field light generator including awaveguide and a plasmon generator is manufactured. The waveguideincludes a core through which light propagates, and a cladding thatsurrounds the core. The core has a top surface. The cladding includes acladding layer that has a groove located above the top surface of thecore. The groove has two wall faces that intersect at a predeterminedangle. The plasmon generator has: two slopes that are opposed to the twowall faces; an edge part defined by the two slopes intersecting eachother; and a near-field light generating part located at an end of theedge part and generating near-field light. The light propagating throughthe core is totally reflected at the top surface of the core to causeevanescent light to occur from the top surface of the core. A surfaceplasmon is excited on the edge part through coupling with the evanescentlight, and the surface plasmon propagates along the edge part to thenear-field light generating part. The near-field light generating partgenerates near-field light based on the surface plasmon.

The method of manufacturing the near-filed light generator of thepresent invention includes the steps of: forming the core; forming thecladding; and forming the plasmon generator. The step of forming thecladding includes the steps of: forming a layer to be etched that ismade of a dielectric material and has a top surface; forming an etchingmask on the top surface of the layer to be etched, the etching maskhaving an opening; and taper-etching a portion of the layer to beetched, the portion being exposed from the opening, by reactive ionetching so that the groove is formed in the layer to be etched and thelayer to be etched thereby becomes the cladding layer. The step oftaper-etching employs an etching gas containing a first gas contributingto the etching of the layer to be etched and a second gas contributingto deposition of a sidewall protective film, and changes, during thestep, the ratio of the flow rate of the second gas to the flow rate ofthe first gas so that the ratio increases.

In the taper-etching method and the method of manufacturing thenear-field light generator of the present invention, the step oftaper-etching may increase the ratio of the flow rate of the second gasto the flow rate of the first gas in a stepwise or stepless manner.

In the taper-etching method and the method of manufacturing thenear-field light generator of the present invention, the first gas maycontain Cl₂ and BCl₃.

In the taper-etching method and the method of manufacturing thenear-field light generator of the present invention, the layer to beetched may be made of Al₂O₃, and the second gas may contain at least oneof N₂ and CF₄.

In the taper-etching method and the method of manufacturing thenear-field light generator of the present invention, the layer to beetched may be made of SiO₂ or SiON, the etching mask may containelemental Al, and the second gas may contain N₂.

In the taper-etching method of the present invention, the ratio of theflow rate of the second gas contributing to the deposition of thesidewall protective film to the flow rate of the first gas contributingto the etching of the layer to be etched is changed during the step oftaper-etching so that the ratio increases. As the etching proceeds inthe layer to be etched, the depth of the groove being etched increasesand the distance between the two sidewalls at the bottom of the groovedecreases. In this situation, according to the present invention, it ispossible that in a region near the bottom of the groove, the advancementof the etching can be retarded and the formation of the sidewallprotective film can be accelerated so as to prevent the etching frombecoming predominant over the deposition of the sidewall protectivefilm. The present invention thus makes it possible to form, in a layerto be etched that is made of a dielectric material, a groove having twowall faces that each form a constant or almost constant inclinationangle from the opening to lower end of the groove and that intersect ata predetermined angle.

According to the method of manufacturing the near-field light generatorof the present invention, the aforementioned operation makes it possibleto form the cladding layer by forming, in a layer to be etched that ismade of a dielectric material, a groove located above the top surface ofthe core and having two wall faces that each form a constant or almostconstant inclination angle from the opening to lower end of the grooveand that intersect at a predetermined angle.

Other and further objects, features and advantages of the presentinvention will appear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view showing part of the medium facing surface of athermally-assisted magnetic recording head of a first embodiment of theinvention.

FIG. 2 is a cross-sectional view showing the configuration of thethermally-assisted magnetic recording head of the first embodiment ofthe invention.

FIG. 3 is a front view showing the medium facing surface of thethermally-assisted magnetic recording head of the first embodiment ofthe invention.

FIG. 4 is a plan view showing a first layer of a coil of thethermally-assisted magnetic recording head of the first embodiment ofthe invention.

FIG. 5 is a plan view showing a second layer of the coil of thethermally-assisted magnetic recording head of the first embodiment ofthe invention.

FIG. 6 is a cross-sectional view showing a step of a method ofmanufacturing a near-field light generator according to the firstembodiment of the invention.

FIG. 7 is a cross-sectional view showing a step that follows the stepshown in FIG. 6.

FIG. 8 is a cross-sectional view showing a step that follows the stepshown in FIG. 7.

FIG. 9 is a cross-sectional view showing a step that follows the stepshown in FIG. 8.

FIG. 10 is a cross-sectional view showing a step that follows the stepshown in FIG. 9.

FIG. 11 is a cross-sectional view showing a step that follows the stepshown in FIG. 10.

FIG. 12 is a cross-sectional view showing a step of an etching method ofa comparative example.

FIG. 13 is an explanatory diagram illustrating an etching by reactiveion etching.

FIG. 14 is a cross-sectional view showing a step of a method ofmanufacturing a near-field light generator according to a secondembodiment of the invention.

FIG. 15 is a cross-sectional view showing a step that follows the stepshown in FIG. 14.

FIG. 16 is a cross-sectional view showing a step that follows the stepshown in FIG. 15.

FIG. 17 is a cross-sectional view showing a step that follows the stepshown in FIG. 16.

FIG. 18 is a cross-sectional view showing a step that follows the stepshown in FIG. 17.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiments

Preferred embodiments of the present invention will now be described indetail with reference to the drawings. First, reference is made to FIG.1 to FIG. 3 to describe the configuration of a thermally-assistedmagnetic recording head of a first embodiment of the invention. FIG. 1is a front view showing part of the medium facing surface of thethermally-assisted magnetic recording head. FIG. 2 is a cross-sectionalview showing the configuration of the thermally-assisted magneticrecording head. FIG. 3 is a front view showing the medium facing surfaceof the thermally-assisted magnetic recording head.

The thermally-assisted magnetic recording head of the present embodimentis for use in perpendicular magnetic recording, and is in the form of aslider to fly over the surface of a recording medium that rotates. Whenthe recording medium rotates, an airflow passing between the recordingmedium and the slider causes a lift to be exerted on the slider. Theslider is configured to fly over the surface of the recording medium bymeans of the lift.

As shown in FIG. 2, the thermally-assisted magnetic recording head has amedium facing surface 40 that faces the recording medium. Here, Xdirection, Y direction, and Z direction will be defined as follows. TheX direction is the direction across the tracks of the recording medium,i.e., the track width direction. The Y direction is a directionperpendicular to the medium facing surface 40. The Z direction is thedirection of travel of the recording medium as viewed from the slider.The X, Y, and Z directions are orthogonal to one another.

As shown in FIG. 2 and FIG. 3, the thermally-assisted magnetic recordinghead includes: a substrate 1 made of a ceramic material such as aluminumoxide-titanium carbide (Al₂O₃—TiC) and having a top surface 1 a: aninsulating layer 2 made of an insulating material and disposed on thetop surface 1 a of the substrate 1; and a bottom shield layer 3 made ofa magnetic material and disposed on the insulating layer 2. Theinsulating layer 2 is made of alumina (Al₂O₃), for example. The Zdirection is also a direction perpendicular to the top surface 1 a ofthe substrate 1.

The thermally-assisted magnetic recording head further includes: abottom shield gap film 4 which is an insulating film disposed on the topsurface of the bottom shield layer 3; a magnetoresistive (MR) element 5serving as a read element disposed on the bottom shield gap film 4; twoleads (not shown) connected to the MR element 5; and a top shield gapfilm 6 which is an insulating film disposed on the MR element 5.

An end of the MR element 5 is located in the medium facing surface 40facing the recording medium. The MR element 5 may be an element made ofa magneto-sensitive film that exhibits a magnetoresistive effect, suchas an anisotropic magnetoresistive (AMR) element, a giantmagnetoresistive (GMR) element, or a tunneling magnetoresistive (TMR)element. The GMR element may be of either the current-in-plane (CIP)type in which a current used for detecting magnetic signals is fed in adirection generally parallel to the plane of layers constituting the GMRelement or the current-perpendicular-to-plane (CPP) type in which thecurrent used for detecting magnetic signals is fed in a directiongenerally perpendicular to the plane of layers constituting the GMRelement.

The thermally-assisted magnetic recording head further includes: areturn pole layer 10 made of a magnetic material and disposed on the topshield gap film 6; a not-shown insulating layer disposed on the topshield gap film 6 and surrounding the return pole layer 10; and aninsulating layer 11 disposed on part of the top surface of the returnpole layer 10. The not-shown insulating layer and the insulating layer11 are made of alumina, for example.

The thermally-assisted magnetic recording head further includes: ashield layer 12 made of a magnetic material and disposed on the returnpole layer 10 in the vicinity of the medium facing surface 40; acoupling layer 13 made of a magnetic material and disposed on the returnpole layer 10 at a position that is farther from the medium facingsurface 40 than is the position of the shield layer 12; and aninsulating layer 14 disposed around the shield layer 12 and the couplinglayer 13. The shield layer 12 has an end face located in the mediumfacing surface 40. The insulating layer 14 is made of alumina, forexample.

The thermally-assisted magnetic recording head further includes acoupling layer 15 made of a magnetic material and disposed on thecoupling layer 13, and an insulating layer 16 disposed over the shieldlayer 12 and the insulating layer 14 and surrounding the coupling layer15. The insulating layer 16 is made of alumina, for example. The topsurfaces of the coupling layer 15 and the insulating layer 16 are evenwith each other.

The thermally-assisted magnetic recording head further includes awaveguide including a core 19 and a cladding. The cladding surrounds thecore 19 and includes cladding layers 18, 20, and 21. The cladding layer18 lies over the coupling layer 15 and the insulating layer 16. The core19 is disposed on the cladding layer 18. The cladding layer 20 lies onthe cladding layer 18 and surrounds the core 19. The top surfaces of thecore 19 and the cladding layer 20 are even with each other. The claddinglayer 21 lies over the core 19 and the cladding layer 20.

The core 19 has an incidence part 19 a, an end face 19 b that is closerto the medium facing surface 40, and a top surface 19 c. The end face 19b may be located in the medium facing surface 40 or at a distance fromthe medium facing surface 40. FIG. 1 to FIG. 3 show an example where theend face 19 b is located in the medium facing surface 40.

The core 19 includes a first layer 191 and a second layer 192. The firstlayer 191 includes the aforementioned end face 19 b and top surface 19c, and has a bottom surface. The first layer 191 extends in a directionperpendicular to the medium facing surface 40 (the Y direction). Thesecond layer 192 is disposed along the bottom surface of the first layer191 and bonded to the bottom surface. The first layer 191 has anincidence end face 191 a that constitutes a portion of the incidencepart 19 a. The second layer 192 has an incidence end face 192 a thatconstitutes another portion of the incidence part 19 a. Laser lightemitted from a not-shown laser diode is incident on the incidence part19 a and propagates through the core 19. The cladding layers 18, 20 and21 are each formed of a dielectric material that has a refractive indexlower than that of the core 19. For example, the core 19 may be formedof tantalum oxide such as Ta₂O₅, or of SiON. The cladding layers 18, 20and 21 may be formed of alumina, SiO₂, or SiON, for example. In thepresent embodiment, the cladding layer 21 is formed of alumina, inparticular.

As shown in FIG. 1, the cladding layer 21 has a top surface 21 a, and agroove 21 b located above the top surface 19 c of the core 19. Thegroove 21 b is V-shaped in cross section parallel to the medium facingsurface 40. The groove 21 b has two wall faces 21 b 1 and 21 b 2 thatintersect at a predetermined angle. The groove 21 b has a lower end thatfaces the top surface 19 c of the core 19 with a predetermined gaptherebetween and that extends in the direction perpendicular to themedium facing surface 40 (the Y direction). Here, as shown in FIG. 1,the angle that each of the two wall faces 21 b 1 and 21 b 2 forms withrespect to the direction perpendicular to the top surface 21 a will bereferred to as the inclination angle and represented by the symbol θ. Inthe present embodiment, in particular, the inclination angle θ of eachof the two wall faces 21 b 1 and 21 b 2 is constant or almost constantfrom the opening to lower end of the groove 21 b. The angle between thetwo wall faces 21 b 1 and 21 b 2 is twice the inclination angle θ of thewall faces 21 b 1 and 21 b 2, that is, 2θ. The angle 2θ preferably fallswithin the range of 50° to 120°, for example. The depth (the dimensionin the Z direction) of the groove 21 b will be represented by the symbolH. The depth H preferably falls within the range of 0.05 to 0.3 μm, forexample.

The thermally-assisted magnetic recording head further includes aplasmon generator 22 and a main pole 23. The plasmon generator 22 isdisposed above the top surface 19 c of the core 19 in the vicinity ofthe medium facing surface 40. The main pole 23 is made of a magneticmaterial and disposed such that the plasmon generator 22 is interposedbetween the core 19 and the main pole 23. At least part of the plasmongenerator 22 is accommodated in the groove 21 b of the cladding layer21. The plasmon generator 22 is made of a metal. More specifically, theplasmon generator 22 is made of, for example, one of Au, Ag, Al, Cu, Pd,Pt, Rh and Ir, or of an alloy composed of two or more of these elements.A detailed description will be made later as to the shapes of theplasmon generator 22 and the main pole 23.

The thermally-assisted magnetic recording head further includes twocoupling portions 17A and 17B embedded in the cladding layers 18, 20 and21 at positions away from the medium facing surface 40. The couplingportions 17A and 17B are made of a magnetic material. The couplingportions 17A and 17B are located on opposite sides of the core 19 in thetrack width direction (the X direction), each being spaced from the core19. Although not shown, each of the coupling portions 17A and 17Bincludes a first layer located on the coupling layer 15, and a secondlayer and a third layer stacked in this order on the first layer.

The thermally-assisted magnetic recording head further includes acoupling layer 24 made of a magnetic material and disposed on thecoupling portions 17A and 17B, and an insulating layer 25 disposed onthe cladding layer 21 and surrounding the main pole 23 and the couplinglayer 24. The insulating layer 25 is made of alumina, for example. Thetop surfaces of the main pole 23, the coupling layer 24, and theinsulating layer 25 are even with each other.

The thermally-assisted magnetic recording head further includes acoupling layer 26 made of a magnetic material and disposed on the mainpole 23, and a coupling layer 27 made of a magnetic material anddisposed on the coupling layer 24.

The thermally-assisted magnetic recording head further includes aninsulating layer 28 disposed on the insulating layer 25, a plurality offirst coil elements 30A disposed on the insulating layer 28, aninsulating layer 31 disposed around the plurality of first coil elements30A, an insulating layer 32 disposed to cover the plurality of firstcoil elements 30A and the insulating layer 31, and an insulating layer33 disposed around the coupling layers 26 and 27 and the insulatinglayer 31. FIG. 4 shows the plurality of first coil elements 30A. Theplurality of first coil elements 30A are arranged side by side in the Ydirection. Each first coil element 30A has a main part extending in thetrack width direction (the X direction). Each first coil element 30A ismade of a conductive material such as copper. The insulating layers 28and 31 to 33 are made of alumina, for example.

The thermally-assisted magnetic recording head further includes a yokelayer 34 made of a magnetic material and disposed over the couplinglayers 26 and 27 and the insulating layer 32, and an insulating layer 35disposed around the yoke layer 34. The yoke layer 34 magneticallycouples the coupling layer 26 to the coupling layer 27. The insulatinglayer 35 is made of alumina, for example. The top surfaces of the yokelayer 34 and the insulating layer 35 are even with each other.

The thermally-assisted magnetic recording head further includes: aninsulating layer 36 disposed over the yoke layer 34 and the insulatinglayer 35; a plurality of second coil elements 30B and a lead layer 30Cdisposed on the insulating layer 36; and a protective layer 37 disposedto cover the plurality of second coil elements 30B and the lead layer30C. The insulating layer 36 and the protective layer 37 are made ofalumina, for example.

FIG. 5 shows the plurality of second coil elements 30B and the leadlayer 30C. The plurality of second coil elements 30B are arranged sideby side in the Y direction. Each second coil element 30B has a main partextending in the track width direction (the X direction). Each secondcoil element 30B and the lead layer 30C are made of a conductivematerial such as copper.

As shown in FIG. 4 and FIG. 5, the thermally-assisted magnetic recordinghead further includes a plurality of connection parts 38 and a singleconnection part 39. The plurality of connection parts 38 connect theplurality of first coil elements 30A to the plurality of second coilelements 30B so as to form a coil 30 wound helically around the yokelayer 34. The connection part 39 connects one of the first coil elements30A to the lead layer 30C. The connection parts 38 and the connectionpart 39 are provided to penetrate through the insulating layers 32, 35and 36. The connection parts 38 and the connection part 39 are each madeof a conductive material such as copper.

The parts from the bottom shield layer 3 to the return pole layer 10constitute a read head. The parts from the return pole layer 10 to theplurality of second coil elements 30B constitute a write head. The coil30 is composed of the plurality of first coil elements 30A, theplurality of second coil elements 30B, and the plurality of connectionparts 38. The coil 30 produces a magnetic field corresponding to data tobe written on the recording medium. The shield layer 12, the return polelayer 10, the coupling layers 13 and 15, the coupling portions 17A and17B, the coupling layers 24 and 27, the yoke layer 34, the couplinglayer 26, and the main pole 23 form a magnetic path for passing amagnetic flux corresponding to the magnetic field produced by the coil30. The main pole 23 allows the magnetic flux corresponding to themagnetic field produced by the coil 30 to pass, and produces a writemagnetic field for writing data on the recording medium by means of aperpendicular magnetic recording system.

As has been described, the thermally-assisted magnetic recording head ofthe present embodiment includes the medium facing surface 40, the readhead, and the write head. The medium facing surface 40 faces therecording medium. The read head and the write head are stacked on thesubstrate 1. Relative to the read head, the write head is located on theforward side (the trailing side) in the direction of travel of therecording medium (the Z direction).

The read head includes the MR element 5 serving as a read element, andthe bottom shield layer 3 and a top shield layer for shielding the MRelement 5. The bottom shield layer 3 and the top shield layer have theirrespective portions that are located near the medium facing surface 40and opposed to each other with the MR element 5 therebetween. In thepresent embodiment, the return pole layer 10 of the write head alsoserves as the top shield layer of the read head. The read head furtherincludes the bottom shield gap film 4 disposed between the MR element 5and the bottom shield layer 3, and the top shield gap film 6 disposedbetween the MR element 5 and the return pole layer 10.

The write head includes the coil 30, the main pole 23, the waveguide,and the plasmon generator 22. The waveguide includes the core 19 and thecladding. The cladding includes the cladding layers 18, 20, and 21. Thecoil 30 produces a magnetic field corresponding to data to be written onthe recording medium. The main pole 23 allows a magnetic fluxcorresponding to the magnetic field produced by the coil 30 to pass, andproduces a write magnetic field for writing data on the recording mediumby means of the perpendicular magnetic recording system.

The near-field light generator according to the present embodimentincludes the waveguide including the core 19 and the cladding, andincludes the plasmon generator 22. The core 19 has the top surface 19 cand propagates laser light emitted from a not-shown laser diode. Thecladding includes the cladding layer 21 having the groove 21 b locatedabove the top surface 19 c of the core 19. The groove 21 b has the twowall faces 21 b 1 and 21 b 2 that each form a constant or almostconstant inclination angle θ from the opening to lower end of the groove21 b and that intersect at a predetermined angle 2θ. At least part ofthe plasmon generator 22 is located in the groove 21 b.

Now, with reference to FIG. 1, an example of the shape of the plasmongenerator 22 and the main pole 23 will be described in detail below. Inthe example shown in FIG. 1, the plasmon generator 22 has two slopes 22a and 22 b, an edge part 22 e, and a near-field light generating part 22g. The two slopes 22 a and 22 b are opposed to the two wall faces 21 b 1and 21 b 2 of the groove 21 b of the cladding layer 21. The edge part 22e is defined by the two slopes 22 a and 22 b intersecting each other.The near-field light generating part 22 g lies at an end of the edgepart 22 e and generates near-field light. The edge part 22 e faces thetop surface 19 c of the core 19 with a predetermined gap therebetween,and extends in the direction perpendicular to the medium facing surface40 (the Y direction). The near-field light generating part 22 g islocated in the medium facing surface 40. The angle between the twoslopes 22 a and 22 b is equal to the angle 2θ between the two wall faces21 b 1 and 21 b 2 of the groove 21 b.

The plasmon generator 22 further has a sidewall part 221A including theslope 22 a, a sidewall part 221B including the slope 22 b, and extendedportions 222A and 222B that are coupled to the upper ends of thesidewall parts 221A and 221B, respectively. The sidewall parts 221A and221B and the extended portions 222A and 222B are each plate-shaped. Thesidewall part 221A is disposed along the wall face 21 b 1 of the groove21 b. The sidewall part 221B is disposed along the wall face 21 b 2 ofthe groove 21 b. The extended portions 222A and 222B are disposed alongthe top surface 21 a of the cladding layer 21. The extended portion 222Aextends from the upper end of the sidewall part 221A in a direction awayfrom both the sidewall parts 221A and 221B. The extended portion 222Bextends from the upper end of the sidewall part 221B in a direction awayfrom both the sidewall parts 221A and 221B.

The main pole 23 includes a first portion 231 and a second portion 232.The first portion 231 is accommodated in the space defined by the twosidewall parts 221A and 221B of the plasmon generator 22. The secondportion 232 is located farther from the core 19 than is the firstportion 231. In FIG. 1, the border between the first portion 231 and thesecond portion 232 is shown by chain double-dashed lines.

The shapes and the arrangement of the plasmon generator 22 and the mainpole 23 are not limited to the foregoing example that has been describedwith reference to FIG. 1.

Now, the principle of generation of near-field light in the presentembodiment and the principle of thermally-assisted magnetic recordingusing the near-field light will be described in detail. Laser lightemitted from a not-shown laser diode is incident on the incidence part19 a of the core 19. As shown in FIG. 2, the laser light 50 propagatesthrough the core 19 toward the medium facing surface 40, and reaches thevicinity of the plasmon generator 22. The laser light 50 is then totallyreflected at the top surface 19 c of the core 19. This causes evanescentlight to occur from the top surface 19 c to permeate into the claddinglayer 21. As a result, surface plasmons are excited at least on the edgepart 22 e in the plasmon generator 22 through coupling with theevanescent light.

The surface plasmons excited on the plasmon generator 22 propagate alongthe edge part 22 e to the near-field light generating part 22 g.Consequently, the surface plasmons concentrate at the near-field lightgenerating part 22 g, and near-field light occurs from the near-fieldlight generating part 22 g based on the surface plasmons. The near-fieldlight is projected toward the recording medium, reaches the surface ofthe recording medium and heats a part of the magnetic recording layer ofthe recording medium. This lowers the coercivity of the part of themagnetic recording layer. In thermally-assisted magnetic recording, thepart of the magnetic recording layer with the lowered coercivity issubjected to a write magnetic field produced by the main pole 23 fordata writing.

Now, with reference to FIG. 2 and FIG. 3, a description will be given ofa method of manufacturing the thermally-assisted magnetic recording headof the present embodiment. The method of manufacturing thethermally-assisted magnetic recording head of the present embodimentincludes the steps of; forming components of a plurality ofthermally-assisted magnetic recording heads other than the substrates 1on a substrate that includes portions to become the substrates 1 of theplurality of thermally-assisted magnetic recording heads, therebyfabricating a substructure that includes rows of a plurality of pre-headportions that are to later become the plurality of thermally-assistedmagnetic recording heads; and forming the plurality ofthermally-assisted magnetic recording heads by cutting the substructureto separate the plurality of pre-head portions from each other. In thestep of forming the plurality of thermally-assisted magnetic recordingheads, the cut surfaces are polished into the medium facing surfaces 40.

The method of manufacturing the thermally-assisted magnetic recordinghead of the present embodiment will now be described in more detail withattention focused on a single thermally-assisted magnetic recordinghead. In the method of manufacturing the thermally-assisted magneticrecording head of the present embodiment, the insulating layer 2 isformed on the substrate 1 first. Next, the bottom shield layer 3 isformed on the insulating layer 2. The bottom shield gap film 4 is thenformed on the bottom shield layer 3. Next, the MR element 5 andnot-shown two leads connected to the MR element 5 are formed on thebottom shield gap film 4. The top shield gap film 6 is then formed tocover the MR element 5 and the leads.

Next, the return pole layer 10 is formed on the top shield gap film 6.Next, a not-shown insulating layer is formed to cover the return polelayer 10. The not-shown insulating layer is then polished by, forexample, chemical mechanical polishing (hereinafter referred to as CMP),until the return pole layer 10 is exposed. Then, the insulating layer 11is formed on part of the top surface of the return pole layer 10.

Next, the shield layer 12 and the coupling layer 13 are formed on thereturn pole layer 10. Next, the insulating layer 14 is formed to coverthe shield layer 12 and the coupling layer 13. The insulating layer 14is then polished by, for example, CMP, until the shield layer 12 and thecoupling layer 13 are exposed.

Next, the coupling layer 15 is formed on the coupling layer 13. Next,the insulating layer 16 is formed to cover the coupling layer 15. Theinsulating layer 16 is then polished by, for example, CMP, until thecoupling layer 15 is exposed. The top surfaces of the coupling layer 15and the insulating layer 16 are thereby made even with each other.

Next, the first layers of the coupling portions 17A and 17B are formedon the coupling layer 15. The cladding layer 18 is then formed to coverthe first layers of the coupling portions 17A and 17B. The claddinglayer 18 is then polished by, for example, CMP, until the first layersof the coupling portions 17A and 17B are exposed.

Next, the core 19 is formed on the cladding layer 18. The second layersof the coupling portions 17A and 17B are formed on the first layers ofthe coupling portions 17A and 17B. The cladding layer 20 is then formedto cover the core 19 and the second layers of the coupling portions 17Aand 17B. The cladding layer 20 is then polished by, for example, CMP,until the core 19 and the second layers of the coupling portions 17A and17B are exposed.

Next, the third layers of the coupling portions 17A and 17B are formedon the second layers of the coupling portions 17A and 17B. The claddinglayer 21, the plasmon generator 22, and the main pole 23 are then formedin this order. The plasmon generator 22 is formed by initially forming ametal film by, for example, sputtering, and then patterning the metalfilm. The main pole 23 is formed by plating, for example. The step offorming the cladding layer 21 will be described in detail later.

Next, the coupling layer 24 is formed over the third layers of thecoupling portions 17A and 17B. Next, the insulating layer 25 is formedto cover the main pole 23 and the coupling layer 24. The insulatinglayer 25 is then polished by, for example, CMP, until the main pole 23and the coupling layer 24 are exposed.

Next, the insulating layer 28 is formed over the main pole 23, thecoupling layer 24, and the insulating layer 25. The plurality of firstcoil elements 30A are then formed on the insulating layer 28. Next, theinsulating layer 31 is formed around the first coil elements 30A. Theinsulating layer 32 is then formed to cover the plurality of first coilelements 30A and the insulating layer 31. Next, the insulating layers28, 31 and 32 are selectively etched to form therein openings forexposing the top surface of the main pole 23 and openings for exposingthe top surface of the coupling layer 24. Then, the coupling layer 26 isformed on the main pole 23, and the coupling layer 27 is formed on thecoupling layer 24. Next, the insulating layer 33 is formed to cover thecoupling layers 26 and 27. The insulating layer 33 is then polished by,for example, CMP, until the coupling layers 26 and 27 are exposed.

Next, the insulating layer 32 is selectively etched to form therein aplurality of openings for passing portions of the connection parts 38and 39. The connection parts 38 and 39 are then formed to be connectedto the plurality of first coil elements 30A through the plurality ofopenings. The yoke layer 34 is formed over the coupling layers 26 and 27and the insulating layer 32. Next, the insulating layer 35 is formed tocover the yoke layer 34 and the connection parts 38 and 39. Theinsulating layer 35 is then polished by, for example, CMP, until theyoke layer 34 and the connection parts 38 and 39 are exposed. Next, theinsulating layer 36 is formed over the yoke layer 34, the insulatinglayer 35, and the connection parts 38 and 39.

Next, the insulating layer 36 is selectively etched to form therein aplurality of openings for exposing the top surfaces of the connectionparts 38 and 39. The plurality of second coil elements 30B and the leadlayer 30C are then formed on the insulating layer 36 and the connectionparts 38 and 39. Next, the protective layer 37 is formed to cover theplurality of second coil elements 30B and the lead layer 30C. Wiring,terminals, and other components are then formed on the top surface ofthe protective layer 37.

When the substructure is completed thus, the substructure is cut toseparate the plurality of pre-head portions from each other, and thenpolishing of the medium facing surface 40, fabrication of flying rails,and other processing are performed to complete the thermally-assistedmagnetic recording head.

Now, the method of manufacturing the near-field light generatoraccording to the present embodiment will be described. The method ofmanufacturing the near-field light generator according to the presentembodiment includes the steps of; forming the core 19; forming thecladding; and forming the plasmon generator 22. The step of forming thecladding includes the steps of; forming the cladding layer 18; formingthe cladding layer 20; and forming the cladding layer 21.

Reference is now made to FIG. 6 to FIG. 11 to describe the step offorming the cladding layer 21. In the present embodiment, the claddinglayer 21 is formed of alumina. The following includes the description ofthe taper-etching method according to the present embodiment. FIG. 6 toFIG. 11 each show a cross section of a stack of layers formed in theprocess of manufacturing the near-field light generator, the crosssection being taken in the position where the medium facing surface 40is to be formed.

FIG. 6 shows a step that follows the formation of the third layers ofthe coupling portions 17A and 17B. In this step, a layer to be etched21P is formed first. The layer to be etched 21P is made of a dielectricmaterial. The layer to be etched 21P is formed by initially forming adielectric material layer to cover the top surface 19 c of the core 19,the top surface of the cladding layer 20 and the third layers of thecoupling portions 17A and 17B, and then polishing the dielectricmaterial layer by, for example, CMP, until the third layers of thecoupling portions 17A and 17B are exposed. The groove 21 b, which isV-shaped in cross section parallel to the medium facing surface 40, isto be formed later in the layer to be etched 21P. The layer to be etched21P becomes the cladding layer 21 when the groove 21 b is formed. Thelayer to be etched 21P has a top surface 21Pa. In the presentembodiment, the dielectric material to form the layer to be etched 21P(the dielectric material layer) is alumina, in particular. On the topsurface 21Pa of the layer to be etched 21P, an etching mask materiallayer 51P of Ta is then formed. The etching mask material layer 51P hasa thickness in the range of 2 to 60 nm, for example.

FIG. 7 shows the next step. In this step, an etching mask 52 is formedon the top surface of the etching mask material layer 51P. The etchingmask 52 has an opening 52 a having a shape corresponding to the planarshape of the groove 21 b to be formed later. The etching mask 52 isformed by patterning a photoresist layer by photolithography. Theminimum width (critical dimension) of the opening 52 a is the width inthe X direction, and falls within the range of 0.15 to 0.5 μm, forexample. The thicker the etching mask 52, the less controllable theminimum width of the opening 52 a becomes. Thus, the thickness of theetching mask 52 is preferably reduced to some extent. The etchingselectivity of the etching mask 52 relative to the layer to be etched21P made of alumina is, for example, 0.5 or less. Accordingly, takinginto account the depth H of the groove 21 b to be formed in the layer tobe etched 21P, the thickness of the etching mask 52 is preferably 0.6 μmor greater. By way of example, where the minimum width of the opening 52a is within the range of 0.2 to 0.3 μm, the thickness of the etchingmask 52 is 1 μm. However, the thickness of the etching mask 52 need notalways be 1 μm.

Next, a portion of the etching mask material layer 51P that is exposedfrom the opening 52 a is etched by, for example, reactive ion etching(hereinafter referred to as RIE) using the etching mask 52. Thisprovides the etching mask material layer 51P with an opening 51 a havinga shape corresponding to the planar shape of the groove 21 b to beformed later. The etching mask material layer 51P thereby becomes anetching mask 51. In the present embodiment, the etching masks 51 and 52correspond to the etching mask according to the invention.

Next, the groove 21 b is formed in the layer to be etched 21P so thatthe layer to be etched 21P becomes the cladding layer 21. In the step offorming the groove 21 b, a portion of the layer to be etched 21P that isexposed from the opening 51 a of the etching mask 51 and the opening 52a of the etching mask 52 is taper-etched by RIE using the etching masks51 and 52. The etching masks 51 and 52 are then removed.

The step of taper-etching the layer to be etched 21P by RIE employs anetching gas containing a first gas that contributes to the etching ofthe layer to be etched 21P and a second gas that contributes to thedeposition of a sidewall protective film. The first gas may contain Cl₂and BCl₃. The second gas may contain at least one of N₂ and CF₄.

Where the second gas contains N₂, elemental Al contained in the layer tobe etched 21P made of alumina and elemental N contained in the etchinggas produce a reaction product AlN during the etching of the layer to beetched 21P. Where the second gas contains CF4, elemental Al contained inthe layer to be etched 21P made of alumina and elemental F contained inthe etching gas produce a reaction product AlF during the etching of thelayer to be etched 21P. Such a reaction product adheres to the sidewallsof the groove formed in the layer to be etched 21P to form a sidewallprotective film. The sidewall protective film made of the reactionproduct is deposited on the sidewalls of the groove being formed by theetching, and the groove 21 b is thereby formed.

In the step of taper-etching the layer to be etched 21P by RIE, each ofthe two wall faces 21 b 1 and 21 b 2 of the groove 21 b is formed to beinclined at an inclination angle θ with respect to the directionperpendicular to the top surface 21Pa of the layer to be etched 21P (thetop surface 21 a of the cladding layer 21). In this manner, there isformed the groove 21 b which is V-shaped in cross section parallel tothe medium facing surface 40 and has the two wall faces 21 b 1 and 21 b2 intersecting at a predetermined angle 2θ. The groove 21 b is formednot to reach the top surface 19 c of the core 19. The layer to be etched21P becomes the cladding layer 21 when the groove 21 b is formed.

The inclination angle θ depends on the ratio of the deposition rate ofthe sidewall protective film to the etching rate of the layer to beetched 21P. In the present embodiment, the ratio of the flow rate of thesecond gas to the flow rate of the first gas is controlled in the stepof taper-etching the layer to be etched 21P by RIE, so that theinclination angle θ of each of the two wall faces 21 b 1 and 21 b 2 willbe constant or almost constant from the opening to lower end of thegroove 21 b. More specifically, the ratio of the flow rate of the secondgas to the flow rate of the first gas is changed during this step sothat the ratio increases. This ratio may be increased in a stepwise orstepless manner. The control of the ratio is accomplished by changing atleast one of the flow rate of the first gas and the flow rate of thesecond gas.

Reference is now made to FIG. 8 to FIG. 11 to describe an example wherethe inclination angle θ of each of the wall faces 21 b 1 and 21 b 2 ofthe groove 21 b is made to be 45° so that the angle 2θ is 90°. In thisexample, the step of taper-etching the layer to be etched 21P by RIEincludes first to fourth steps that employ mutually different ratios ofthe flow rate of the second gas to the flow rate of the first gas. Thefirst step lasts for a predetermined duration from the start of etchingof the layer to be etched 21P. The second step lasts for a predeterminedduration after the first step. The third step lasts for a predeterminedduration after the second step. The fourth step lasts for apredetermined duration after the third step and is the final step in theetching of the layer to be etched 21P. FIG. 8 shows the groove after thefirst step. FIG. 9 shows the groove after the second step. FIG. 10 showsthe groove after the third step. FIG. 11 shows the groove after thefourth step, that is, the groove 21 b.

In this example, the first gas contains Cl₂ and BCl₃ and the second gascontains at least one of N₂ and CF₄. Now, a description will be given ofa first example and a second example of the method for controlling theratio of the flow rate of the second gas to the flow rate of the firstgas. The first example changes the flow rate of N₂ whereas secondexample changes the flow rate of CF₄. The first example will bedescribed first. In the first example, the flow rates of Cl₂, BCl₃, andCF₄ are set to 15 sccm, 60 sccm, and 9 sccm, respectively. Furthermore,the flow rate of N₂ is increased in a stepwise manner so as to be 5 sccmin the first step, 11 sccm in the second step, 15 sccm in the thirdstep, and 20 sccm in the fourth step. In this manner, the ratio of theflow rate of the second gas to the flow rate of the first gas isincreased stepwise.

In the first step, as shown in FIG. 8, the portion of the layer to beetched 21P that is exposed from the openings 51 a and 52 a of theetching masks 51 and 52 is etched to form a groove 21Pb in the layer tobe etched 21P. The groove 21Pb has two sidewalls each inclined at apredetermined inclination angle, and a bottom which connects the twosidewalls to each other. In the second to the fourth steps, as shown inFIG. 9 to FIG. 11, etching proceeds in the layer to be etched 21P togradually increase the depth of the groove 21Pb and gradually decreasethe distance between the two sidewalls at the bottom of the groove 21Pb.As a result of the fourth step, the two sidewalls of the groove 21Pbmeets each other at the bottom of the groove 21Pb to form the groove 21b having the wall faces 21 b 1 and 21 b 2 which are inclined at 45° fromthe opening to lower end of the groove 21 b.

The second example will now be described. In the second example, theflow rates of Cl₂, BCl₃, and N₂ are set to 15 sccm, 60 sccm, and 0 sccm,respectively. Furthermore, the flow rate of CF₄ is increased in astepwise manner so as to be 11 sccm in the first step, 14 sccm in thesecond step, 17 sccm in the third step, and 25 sccm in the fourth step.In this manner, the ratio of the flow rate of the second gas to the flowrate of the first gas is increased stepwise. In the second example, asin the first example, etching proceeds in the layer to be etched 21P asshown in FIG. 8 to FIG. 11 so that the groove 21 b is finally formed tohave the wall faces 21 b 1 and 21 b 2 which are inclined at 45° from theopening to lower end of the groove 21 b.

Possible methods for controlling the ratio of the flow rate of thesecond gas to the flow rate of the first gas are not limited to theaforementioned first and second examples. For example, to increase theratio of the flow rate of the second gas to the flow rate of the firstgas in a stepwise manner, the step of taper-etching the layer to beetched 21P by RIE may include two, three, or five or more steps thatemploy mutually different ratios of the flow rate of the second gas tothe flow rate of the first gas. On the other hand, to increase the ratioof the flow rate of the second gas to the flow rate of the first gas ina stepless manner, the step of taper-etching the layer to be etched 21Pby RIE may steplessly decrease the flow rate of the first gas orsteplessly increase the flow rate of the second gas. For example, in theaforementioned first example, the flow rate of N₂ may be steplesslyincreased from 5 sccm to 20 sccm.

As has been described, the step of forming the cladding layer 21 in themethod of manufacturing the near-field light generator according to thepresent embodiment and the taper-etching method according to the presentembodiment include the steps of: forming the layer to be etched 21P thatis made of a dielectric material and has the top surface 21Pa; formingthe etching masks 51 and 52 having the openings 51 a and 52 a on the topsurface 21Pa of the layer to be etched 21P; and taper-etching theportion of the layer to be etched 21P that is exposed from the openings51 a and 52 a, by RIE to form the groove 21 b in the layer to be etched21P so that the layer to be etched 21P becomes the cladding layer 21.

The step of taper-etching the layer to be etched 21P by RIE employs anetching gas containing a first gas contributing to the etching of thelayer to be etched 21P and a second gas contributing to the depositionof the sidewall protective film, and changes, during the step, the ratioof the flow rate of the second gas to the flow rate of the first gas sothat the ratio increases. As the etching proceeds in the layer to beetched 21P, the depth of the groove 21Pb being etched increases and thedistance between the two sidewalls at the bottom of the groovedecreases. In this situation, according to the present embodiment, it ispossible that in a region near the bottom of the groove the advancementof the etching can be retarded and the formation of the sidewallprotective film can be accelerated so as to prevent the etching frombecoming predominant over the deposition of the sidewall protectivefilm. The present embodiment thus makes it possible to form, in thelayer to be etched 21P made of a dielectric material, the groove 21 bhaving the two wall faces 21 b 1 and 21 b 2 that each form a constant oralmost constant inclination angle θ from the opening to lower end of thegroove 21 b and that intersect at a predetermined angle 2θ. Inparticular, the present embodiment allows the groove 21 b to be formedsuch that the inclination angle θ of each of the two wall faces 21 b 1and 21 b 2 falls within the range of 25° to 60°, and consequently theangle 2θ falls within the range of 50° to 120°. Note that the reason whyeach of the two wall faces 21 b 1 and 21 b 2 forms a constant or almostconstant inclination angle θ from the opening to lower end of the groove21 b will be described in detail later.

The angle between the two slopes 22 a and 22 b of the plasmon generator22 affects the intensity of surface plasmons excited on the plasmongenerator 22 and the spot diameter of near-field light generated fromthe near-field light generating part 22 g. In order to increase to someextent the intensity of surface plasmons excited on the plasmongenerator 22 and to decrease to some extent the spot diameter ofnear-field light generated from the near-field light generating part 22g, the angle between the two slopes 22 a and 22 b preferably fallswithin the range of 50° to 120°.

Since the present embodiment allows the groove 21 b of the claddinglayer 21 to be formed as described above, it is possible to form thesidewall parts 221A and 221B of the plasmon generator 22 in the groove21 b such that the angle between the two slopes 22 a and 22 b fallswithin the range of 50° to 120°. Consequently, it is possible to providea near-field light generator configured so that the sidewall parts 221Aand 221B of the plasmon generator 22 are located in the groove 21 b ofthe cladding layer 21 and the angle between the two slopes 22 a and 22 bfalls within the desired range of 50° to 120°.

The effects of the present embodiment will now be described incomparison with an etching method of a comparative example. First, theetching method of the comparative example will be described withreference to FIG. 12. FIG. 12 is a cross-sectional view showing a stepof the etching method of the comparative example. FIG. 12 shows a crosssection of a stack of layers formed in the process of manufacturing anear-field light generator, the cross section being taken in theposition where the medium facing surface 40 is to be formed. In theetching method of the comparative example, the taper-etching of thelayer to be etched 21P by RIE is performed at a constant ratio of theflow rate of the second gas to the flow rate of the first gas in theetching gas. By etching the layer to be etched 21P under such acondition, a groove 121 having two wall faces 121 b 1 and 121 b 2 isformed in the layer 21P. As shown in FIG. 12, the inclination angle ofeach of the wall faces 121 b 1 and 121 b 2 decreases with increasingproximity to the lower end of the groove 121.

Reference is now made to FIG. 13 to describe the reason why the etchingmethod of the comparative example results in the formation of the groove121 having the wall faces 121 b 1 and 121 b 2 whose inclination angledecreases with increasing proximity to the lower end of the groove 121as mentioned above. FIG. 13 is an explanatory diagram illustrating anetching by RIE. In FIG. 13, the numeral 61 represents a layer to beetched, the numeral 62 represents a photoresist mask, and the numeral 63represents ions. The ions 63 travel through a plasma in directions thatare varied to some extent with respect to a direction perpendicular tothe top surface 61 a of the layer to be etched 61. Consequently, therewill occur what is called a shadow region B in the top surface 61 a ofthe layer to be etched 61 in the vicinity of the photoresist mask 62.The shadow region B is a region that the ions 63 are less likely toreach due to the presence of the photoresist mask 62. As a result, arelatively larger amount of ions 63 reach a region A, which is a regionin the top surface 61 a of the layer to be etched 61 that is locatedaway from the photoresist mask 62, as compared with the amount of ions63 that reach the region B. In the region A, a greater amount ofdeposited reaction products are hit by the ions 63 to leave therefromthan in the region B. As a result, in the region A, when compared withthe region B, etching becomes predominant over the deposition of thesidewall protective film. Accordingly, the inclination angle of thesidewalls of the groove formed in the region A becomes smaller than theinclination angle of the sidewalls of the groove formed in the region B.As etching proceeds, the height of the photoresist mask 62 decreases. Asa result, the region B becomes smaller, whereas the region A becomeslarger. For this reason, the phenomenon that the inclination angle ofthe sidewalls of the groove differs depending on the region is morenoticeable when the photoresist mask 62 has a greater height.

As etching proceeds, the depth of the groove being etched graduallyincreases and the distance between the two sidewalls at the bottom ofthe groove gradually decreases. The principle that has been describedwith reference to FIG. 13 holds also true for etching in a region nearthe bottom of the groove. That is, when viewed from a region near thebottom of the groove, the increase in depth of the groove and thedecrease in distance between the two sidewalls at the bottom of thegroove is equivalent to an increase in height of the sidewalls, that is,an increase in height of the photoresist mask 62 in FIG. 13.Accordingly, in the region near the bottom of the groove being etched,the etching becomes predominant over the deposition of the sidewallprotective film as the depth of the groove increases and the distancebetween the two sidewalls at the bottom of the groove decreases. As aresult, as shown in FIG. 12, there is formed the groove 121 having thewall faces 121 b 1 and 121 b 2 whose inclination angle decreases withincreasing proximity to the lower end of the groove 121. Thus, theetching method of the comparative example cannot make the groove 121into a V-shape such that the two wall faces each form a constant oralmost constant inclination angle from the opening to lower end of thegroove 121.

In contrast to this, according to the present embodiment, the step oftaper-etching the layer to be etched 21P by RIE changes the ratio of theflow rate of the second gas contributing to the deposition of thesidewall protective film to the flow rate of the first gas contributingto the etching of the layer to be etched 21P during the step so that theratio increases. Thus, when the depth of the groove 21Pb being etchedincreases and the distance between the two sidewalls at the bottom ofthe groove 21Pb decreases as the etching proceeds in the layer to beetched 21P, it is possible that in a region near the bottom of thegroove the advancement of the etching can be retarded and the formationof the sidewall protective film can be accelerated so as to prevent theetching from becoming predominant over the deposition of the sidewallprotective film. Consequently, according to the present embodiment, itis possible to make the inclination angle θ of each of the two wallfaces 21 b 1 and 21 b 2 be constant or almost constant from the openingto lower end of the groove 21 b.

Second Embodiment

A second embodiment of the invention will now be described. In thethermally-assisted magnetic recording head of the second embodiment, thecladding layer 21 is made of SiO₂ or SiON. The remainder ofconfiguration of the thermally-assisted magnetic recording head of thepresent embodiment is the same as that of the first embodiment.

Now, the method of manufacturing the near-field light generatoraccording to the present embodiment will be described. The step offorming the cladding layer 21 of the present embodiment is differentfrom that of the first embodiment. Reference is now made to FIG. 14 toFIG. 18 to describe the step of forming the cladding layer 21 of thepresent embodiment in detail. The following includes the description ofthe taper-etching method according to the present embodiment. FIG. 14 toFIG. 18 each show a cross section of a stack of layers formed in theprocess of manufacturing the near-field light generator, the crosssection being taken in the position where the medium facing surface 40is to be formed.

FIG. 14 shows a step that follows the formation of the third layers ofthe coupling portions 17A and 17B of the first embodiment shown in FIG.2. In this step, first formed is a layer to be etched 21P that is madeof SiO₂ or SiON. Next, a stopper film 71P of Ru is formed on the topsurface 21Pa of the layer to be etched 21P. Note that any of magneticmaterials, Ni, NiCr, C, MgF, and MgO may be employed instead of Ru.

FIG. 15 shows the next step. In this step, first, an etching maskmaterial layer 72P is formed on the top surface of the stopper film 71P.The etching mask material layer 72P is formed of a material containingelemental Al. The material used to form the etching mask material layer72P may contain at least one of an Al-containing alloy, alumina (Al₂O₃),aluminum nitride (AlN), and aluminum fluoride (AlF), for example. Wherealumina is employed as the material of the etching mask material layer72P, the etching mask material layer 72P is formed to have a thicknessin the range of 0.05 to 0.3 μm, for example.

Next, a photoresist mask 73 is formed on the top surface of the etchingmask material layer 72P. The photoresist mask 73 has an opening 73 athat has a shape corresponding to the planar shape of the groove 21 b tobe formed later. The photoresist mask 73 is formed by patterning aphotoresist layer by photolithography.

FIG. 16 shows the next step. In this step, a portion of the etching maskmaterial layer 72P that is exposed from the opening 73 a is etched byRIE using the photoresist mask 73 as the etching mask. This provides theetching mask material layer 72P with an opening 72 a having a shapecorresponding to the planar shape of the groove 21 b to be formed later.The etching mask material layer 72P thereby becomes an etching mask 72.

Where the etching mask material layer 72P is made of alumina, a gascontaining Cl₂ and BCl₃, for example, is used as the etching gas whenthe etching mask material layer 72P is etched by RIE. The stopper film71P functions as the etching stopper that stops etching when the etchingmask material layer 72P is etched by RIE.

The minimum width (critical dimension) of the opening 72 a is the widthin the X direction, and falls within the range of 0.15 to 0.5 μm, forexample. Where the etching mask material layer 72P is made of alumina,the thicker the etching mask material layer 72P, the less controllablethe minimum width of the opening 72 a becomes. It is thereforepreferable that the thickness of the etching mask material layer 72P be0.3 μm or less. However, the thickness of the etching mask materiallayer 72P need not always be 0.3 μm or less.

Where the etching mask material layer 72P is made of alumina and has athickness of 0.1 μm or less, ion beam etching (hereinafter referred toas IBE) may be employed to etch the etching mask material layer 72P toform the opening 72 a therein.

FIG. 17 shows the next step. In this step, first, a portion of thestopper film 71P that is exposed from the openings 72 a and 73 a isetched away by, for example, IBE or RIE using the etching mask 72 andthe photoresist mask 73 as the etching mask. This provides the stopperfilm 71P with an opening 71 a having a shape corresponding to the planarshape of the groove 21 b to be formed later. The stopper film 71Pthereby becomes an etching mask 71. Next, the photoresist mask 73 isremoved by wet etching or ashing. In the present embodiment, the etchingmasks 71 and 72 correspond to the etching mask according to theinvention.

Where the stopper film 71P is made of Ru, a gas containing O₂ and Cl₂,for example, is used as the etching gas when the stopper film 71P isetched by RIE. Where the etching mask material layer 72P is made ofalumina and has a thickness of 0.1 μm or less, the stopper film 71P maybe etched by IBE simultaneously with the etching of the etching maskmaterial layer 72P.

FIG. 18 shows the next step. In this step, first, the groove 21 b isformed in the layer to be etched 21P so that the layer to be etched 21Pbecomes the cladding layer 21. In the step of forming the groove 21 b, aportion of the layer to be etched 21P that is exposed from the openings71 a and 72 a is taper-etched by RIE using the etching masks 71 and 72.The etching masks 71 and 72 are then removed.

The step of taper-etching the layer to be etched 21P by RIE employs anetching gas containing a first gas and a second gas, the first gascontributing to the etching of the layer to be etched 21P. In thepresent embodiment, since the etching mask 72 is formed of a materialcontaining elemental Al, the entire etching mask consisting of theetching masks 71 and 72 inevitably contains elemental Al. The second gascontains N₂. In this case, a sidewall protective film is formed in thefollowing manner. Part of the etching mask 72 is etched along with thelayer to be etched 21P. Consequently, during the etching of the layer tobe etched 21P, elemental Al contained in the etching mask 72 andelemental N contained in the etching gas produce a reaction product AlN.The reaction product AlN adheres to the sidewalls of the groove formedin the layer to be etched 21P to form the sidewall protective film. Thesidewall protective film made of the reaction product AlN is depositedon the sidewalls of the groove being formed by the etching, and thegroove 21 b is thereby formed.

In the present embodiment, as in the first embodiment, the step oftaper-etching the layer to be etched 21P by RIE changes the ratio of theflow rate of the second gas to the flow rate of the first gas during thestep so that the ratio increases. As such, according to the presentembodiment, it is possible to form the cladding layer 21 by forming, inthe layer to be etched 21P made of SiO₂ or SiON, the groove 21 b havingthe two wall faces 21 b 1 and 21 b 2 that each form a constant or almostconstant inclination angle θ from the opening to lower end of the groove21 b and that intersect at a predetermined angle 2θ.

Here, a description will be given of a case where the inclination angleθ of each of the wall faces 21 b 1 and 21 b 2 is set to 45° so that theangle 2θ is 90° in the example shown in FIG. 18. In this example, thefirst gas contains Cl₂ and BCl₃, while the second gas contains N₂. Theflow rates of Cl₂ and BCl₃ are set to 15 sccm and 60 sccm, respectively.Furthermore, the flow rate of N₂ is increased in a stepwise manner so asto be 9 sccm in the first step, 12 sccm in the second step, 14 sccm inthe third step, and 16 sccm in the fourth step. In this manner, theratio of the flow rate of the second gas to the flow rate of the firstgas is increased stepwise. In this example, as in the first example ofthe first embodiment, etching proceeds in the layer to be etched 21P asshown in FIG. 8 to FIG. 11 so that the groove 21 b is finally formed tohave the wall faces 21 b 1 and 21 b 2 which are inclined at 45° from theopening to lower end of the groove 21 b.

The remainder of configuration, function and effects of the presentembodiment are similar to those of the first embodiment.

The present invention is not limited to the foregoing embodiments, andvarious modifications may be made thereto. For example, thetaper-etching method of the present invention is applicable not only tothe case of forming the groove 21 b in the cladding layer 21 toaccommodate at least part of the plasmon generator 22 as in the methodof manufacturing the near-field light generator of the invention, but toall cases where taper-etching is to be performed on a dielectric layerto be etched.

It is apparent that the present invention can be carried out in variousforms and modifications in the light of the foregoing descriptions.Accordingly, within the scope of the following claims and equivalentsthereof, the present invention can be carried out in forms other thanthe foregoing most preferable embodiments.

What is claimed is:
 1. A taper-etching method for taper-etching a layerto be etched, the layer to be etched being made of a dielectric materialand having a top surface, the taper-etching method comprising the stepsof: forming an etching mask on the top surface of the layer to beetched, the etching mask having an opening; and taper-etching a portionof the layer to be etched, the portion being exposed from the opening,by reactive ion etching so that a groove having two wall faces thatintersect at a predetermined angle is formed in the layer to be etched,wherein: the step of taper-etching employs an etching gas containing afirst gas contributing to the etching of the layer to be etched and asecond gas contributing to deposition of a sidewall protective film, andchanges, during the step, a ratio of a flow rate of the second gas to aflow rate of the first gas so that the ratio increases; the layer to beetched is made of SiO₂ or SiON; the etching mask contains elemental Al;and the second gas contains N₂.
 2. The taper-etching method according toclaim 1, wherein the step of taper-etching increases the ratio of theflow rate of the second gas to the flow rate of the first gas in astepwise manner.
 3. The taper-etching method according to claim 1,wherein the step of taper-etching increases the ratio of the flow rateof the second gas to the flow rate of the first gas in a steplessmanner.
 4. The taper-etching method according to claim 1, wherein thefirst gas contains Cl₂ and BCl₃.
 5. A method of manufacturing anear-field light generator, the near-field light generator comprising awaveguide and a plasmon generator, wherein: the waveguide includes acore through which light propagates, and a cladding that surrounds thecore; the core has a top surface; the cladding includes a cladding layerthat has a groove located above the top surface of the core; the groovehas two wall faces that intersect at a predetermined angle; and theplasmon generator has: two slopes opposed to the two wall faces; an edgepart defined by the two slopes intersecting each other; and a near-fieldlight generating part located at an end of the edge part and generatingnear-field light, the near-field light generator being configured sothat the light propagating through the core is totally reflected at thetop surface of the core to cause evanescent light to occur from the topsurface of the core, and a surface plasmon is excited on the edge partthrough coupling with the evanescent light, the surface plasmonpropagates along the edge part to the near-field light generating part,and the near-field light generating part generates near-field lightbased on the surface plasmon, the method comprising the steps of:forming the core; forming the cladding; and forming the plasmongenerator, wherein: the step of forming the cladding includes the stepsof: forming a layer to be etched, the layer to be etched being made of adielectric material and having a top surface; forming an etching mask onthe top surface of the layer to be etched, the etching mask having anopening; and taper-etching a portion of the layer to be etched, theportion being exposed from the opening, by reactive ion etching so thatthe groove is formed in the layer to be etched and the layer to beetched thereby becomes the cladding layer, wherein: the step oftaper-etching employs an etching gas containing a first gas contributingto the etching of the layer to be etched and a second gas contributingto deposition of a sidewall protective film, and changes, during thestep, a ratio of a flow rate of the second gas to a flow rate of thefirst gas so that the ratio increases; the layer to be etched is made ofSiO₂ or SiON; the etching mask contains elemental Al; and the second gascontains N₂.
 6. The method of manufacturing the near-field lightgenerator according to claim 5, wherein the step of taper-etchingincreases the ratio of the flow rate of the second gas to the flow rateof the first gas in a stepwise manner.
 7. The method of manufacturingthe near-field light generator according to claim 5, wherein the step oftaper-etching increases the ratio of the flow rate of the second gas tothe flow rate of the first gas in a stepless manner.
 8. The method ofmanufacturing the near-field light generator according to claim 5,wherein the first gas contains Cl₂ and BCl₃.